[Broadcast Service Using MBSFN]
In 3rd Generation Partnership Project (3GPP) which is a standardization project of a mobile communication system, Multicast Broadcast Single Frequency Network (MBSFN) is defined as one of functions of Long Term Evolution/System Architecture Evolution (LTE/SAE) (see, for example, NPL 1). FIG. 1 is a diagram illustrating one example of architecture of MBSFN. In addition, FIG. 2 is a diagram illustrating one example of a channel configuration of MBSFN subframe during multicast transmission.
As illustrated in FIG. 1, in a broadcast service using MBSFN, Multi-Cell/Multicast Coordination Entity (MCE) determines whether or not to implement a broadcast service, resources to be used for implementation, Modulation and Coding Scheme (MCS) and the like, and notifies determined information to a base station (also referred to as eNB (Evolved Universal Terrestrial Radio Network (E-UTRAN) Node B)).
In addition, each of a plurality of base stations semi-fixedly (semi-static) notifies notification/update of a subframe (hereinafter, referred to as MBSFN subframe) performing the broadcast service to a connected terminal (also referred to as User Equipment (UE)) using System Information Block (SIB). Then, as illustrated in FIG. 2, the plurality of base stations transmit the same data to the terminal using the same frequency (fc) in the MBSFN subframe.
[Interference Avoidance Technology]
In addition, in 3GPP, enhanced Inter-Cell Interference Coordination (eICIC) technology has been discussed as technology in which the plurality of base stations cooperate to implement inter-cell interference control (see, for example, NPL 1). In eICIC technology, in a case of a subframe (hereinafter, also referred to as LTE subframe) in which one base station performs data transmission (unicast transmission) in the plurality of synchronized base stations, inter-cell interference is avoided by other base stations stopping data transmission.
Further, in eICIC technology, the MBSFN subframe may be used as a subframe (referred to as Almost Blank Subframe (ABS)) for stopping data transmission.
FIG. 3 illustrates an example of a channel configuration in a case where the other base station stops data transmission using the MBSF subframe during one base station is performing unicast transmission. As illustrated in FIG. 3, in a case where data transmission is stopped using the MBSFN subframe, only Cell Reference Signal (CRS) (CRS #0 in FIG. 3) is transmitted in first Orthogonal Frequency-Division Multiplexing (OFDM) symbol, a signal (Physical Downlink Shared Channel (PDSCH) or Physical Downlink Control Channel (PDCCH) is not transmitted in an area other than an area in which CRS is disposed, and the area is configured to be Null.
With this, by stopping data transmission using the MBSFN subframe, that is, by setting the user signal area to Null and transmitting only CRS, it is possible to obtain interference reduction effect more than in a case of stopping data transmission.
PTL 1 discloses a method of controlling switching between MBSFN subframe for multicast providing a broadcast service as illustrated in FIG. 2 and MBSFN subframe for interference avoidance as illustrated in FIG. 3. In PTL 1, one eNB notifies a pattern of MBSFN subframe which is information indicating MBSFN subframe and a pattern of ABS which is information indicating a subframe used for interference avoidance among MBSFN subframes to other eNB through X2 interface which is interface between eNBs. As a result, the MBSFN subframe for multicast and the MBSFN subframe for interference avoidance can be shared as different resource reservation areas between eNBs.